Soy consumption is associated with reduced rates of breast cancer but how soy reduces breast cancer is currently unknown. The quantity and duration of soy consumption needed to achieve an oncoprotective effect of soy on breast cancer is also unknown. The purpose of this study is to find out how much, how long and how often one has to consume soy in order to reduce breast cancer risk. Because breast cancer risk is hypothesized to be associated with excess female hormone levels, we measure female hormone levels after varying amount of soy consumption to determine the potential effectiveness of soy in reducing breast cancer risk.